The present invention relates to heat exchangers of the "dry" type effecting an exchange between a first fluid, such as a gas, steam or liquid, for example water, and a second fluid, for example air, which is separated from the first fluid by a wall.
Such a heat exchanger usually comprises at least one heat exchange wall defining at least partly an inner volume or chamber which communicates with the exterior by way of at least one outlet orifice, the wall comprising an assembly of spaced tubes in which the first fluid flows and wherein the spaces between the tubes provide the passages for the flow of the second fluid.
According to a conventional form of construction, the tubes of such a heat exchanger are made from metal and are usually finned to increase the heat exchange surface. These tubes are united in batteries, each comprising a nest of parallel, usually rectilinear, tubes connected at their ends to a header. For ease of construction and transportation, the batteries of finned tubes are limited in overall size, and this results particularly in large exchangers, in multiplying the number of batteries and hence the number of connections of the tubes to the water-boxes and of the batteries to each other. Consequently, such heat exchangers are very costly.
These metal finned tubes are also highly sensitive to corrosion and to soiling in an industrial atmosphere and it has been proposed to replace the metal finned tubes by smooth tubes of plastics material without, however, departing from the aforementioned traditional assembly method. However, owing to the fact that the heat exchanger surface of a smooth tube is less than that of a finned tube of the same length, it is necessary to increase the number of tubes employed and the number of tube connections. Consequently, this form of construction is just as costly as using finned metal tubes.